Fast and slowly inactivating components of Ca-channel current and their sensitivities to nicardipine in isolated smooth muscle cells from rat vas deferens
- 1 March 1988
- journal article
- research article
- Published by Springer Nature in Pflügers Archiv - European Journal of Physiology
- Vol. 411 (3) , 289-295
- https://doi.org/10.1007/bf00585117
Abstract
(1) Fast and slowly inactivating components of Ca-channel current were compared to clarify whether more than one type of Ca-channel exists in smooth muscle cells from rat vas deferens using the whole cell variant of the patch clamp technique. The pipette was filled with 150 mM Cs solution to eliminate outward current and Ba was used as the charge carrier for Ca-channel current. (2) When activated by a 5 s test pulse to 0 mV from a holding potential of −60 mV, the inactivation process of Ba-current was well fitted by the sum of two exponentials. The time constant of the faster inactivating component was 100–300 ms and that of the slower inactivating component was 1.5–3 s. Steadystate inactivation curves of the fast- and slow-components were very similar. (3) The inward current activated at 0 mV from −80 mV was inactivated faster than that from −30 mV. The voltage-dependencies of the peak current from holding potentials of −30 mV and −80 mV were similar. Both had voltage threshold at −30 mV and were maximal at +10 mV. (4) Low concentrations of nicardipine (10−9 to 10−7 M) preferentially inhibited the slow component while higher concentration (10−6 to 10−5 M) were required to block the fast component. The current activated from a holding potential of −30 mV was almost fully suppressed by 10−7 M nicardipine whereas that from −80 mV was blocked only slightly. The voltage dependencies of the peak currents before and during the superfusion with nicardipine (10−7 M) were similar although the peak amplitude was suppressed in the presence of the drug. (5) These results suggest that the existence of either (a) two populations of Ca channels that differ in the time course of inactivation and the sensitivity to nicardipine, but have nearly identical dependence on membrane potential or (b) one population of Ca channel having two different states of inactivation and the sensitivity of nicardipine, in rat vas deferens.This publication has 41 references indexed in Scilit:
- Calcium and Sodium Channels in Spontaneously Contracting Vascular Muscle CellsScience, 1986
- Properties of two types of calcium channels in clonal pituitary cells.The Journal of general physiology, 1986
- Ca 2+ and Ca 2+ -Activated K + Currents in Mammalian Gastric Smooth Muscle CellsScience, 1985
- Two Distinct Populations of Calcium Channels in a Clonal Line of Pituitary CellsScience, 1985
- A new calcium current underlying the plateau of the cardiac action potentialProceedings of the Royal Society of London. B. Biological Sciences, 1984
- Inactivation of calcium channel current in the calf cardiac Purkinje fiber. Evidence for voltage- and calcium-mediated mechanisms.The Journal of general physiology, 1984
- Na and Ca channels in a transformed line of anterior pituitary cells.The Journal of general physiology, 1984
- Mechanism of calcium channel blockade by verapamil, D600, diltiazem and nitrendipine in single dialysed heart cellsNature, 1983
- Calcium ChannelAnnual Review of Neuroscience, 1981
- Voltage clamp analysis of two inward current mechanisms in the egg cell membrane of a starfish.The Journal of general physiology, 1975